/Engine/Plugins/Experimental/MeshModelingToolsetExp/Source/MeshModelingToolsEditorOnlyExp/Public/BspConversionTool.h
This is the primary event we'll be responding to. It affects whether we can accept or not, and the preview, if it is being shown. Does not affect cached brushes.
void OnEditorSelectionChanged ( [UObject](API\Runtime\CoreUObject\UObject\UObject) * NewSelection )